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United States Patent |
6,053,801
|
Pinson
,   et al.
|
April 25, 2000
|
Substrate polishing with reduced contamination
Abstract
Systems and methods for polishing a substrate with reduced contamination
are described. A rinse arm has one or more nozzles configured to direct
rinse fluid toward a polishing surface for polishing a substrate. The
rinse arm further includes a fluid dispenser configured to direct rinse
fluid to one or more surfaces of the rinse arm in proximity to the
polishing surface and exposed to airborne slurry particles generated from
slurry on the polishing surface. By maintaining the atmosphere in the
vicinity of the exposed rinse arm surfaces at an elevated relative
humidity level, airborne slurry particles adhering to the exposed rinse
arm surfaces remain in suspension and, therefore, may be easily cleaned,
e.g., during a high pressure rinse cycle. This feature reduces the
likelihood that slurry particles will accumulate on exposed surfaces of
the polishing apparatus and flake off while a substrate is being polished,
reducing the likelihood of substrate defects caused by such slurry
contamination.
Inventors:
|
Pinson; Jay D. (San Jose, CA);
Shah; Nitin (Fremont, CA);
Groechel; David W. (Sunnyvale, CA);
Waidl; Joe (San Jose, CA)
|
Assignee:
|
Applied Materials, Inc. (Santa Clara, CA)
|
Appl. No.:
|
309182 |
Filed:
|
May 10, 1999 |
Current U.S. Class: |
451/56; 451/444 |
Intern'l Class: |
B24B 055/12 |
Field of Search: |
451/443,444,56,41,288
|
References Cited
U.S. Patent Documents
5421768 | Jun., 1995 | Fujiwara et al. | 451/287.
|
5578529 | Nov., 1996 | Mullins | 451/41.
|
5616069 | Apr., 1997 | Walker et al. | 451/444.
|
5702563 | Dec., 1997 | Salugsugan et al. | 451/28.
|
5779522 | Jul., 1998 | Walker et al. | 451/444.
|
Foreign Patent Documents |
0010769 | Jan., 1991 | JP | 125/11.
|
Primary Examiner: Rose; Robert A.
Attorney, Agent or Firm: Fish & Richardson
Claims
What is claimed is:
1. A substrate polishing system, comprising:
a substrate carrier;
a polishing surface; and
a rinse arm having one or more nozzles configured to direct rinse fluid
toward the polishing surface, the rinse arm further having a fluid
dispenser configured to direct rinse fluid to one or more surfaces of the
rinse arm in proximity to the polishing surface and exposed to airborne
slurry particles generated from slurry on the polishing surface.
2. The system of claim 1, wherein the fluid dispenser is configured to
direct moist air in the vicinity of the exposed surfaces of the rinse arm.
3. The system of claim 1, wherein the fluid dispenser comprises a nozzle.
4. The system of claim 3, wherein the fluid dispenser is configured to
receive a liquid and to direct the liquid through the nozzle to generate a
fine mist in the vicinity of the one or more exposed surfaces.
5. The system of claim 1, wherein, in operation, the fluid dispenser is
configured to maintain the atmosphere in the vicinity of the one or more
exposed surfaces at a relative humidity level of about 80% or greater.
6. The system of claim 1, wherein, in operation, the fluid dispenser is
configured to maintain a layer of liquid on the one or more exposed
surfaces.
7. The system of claim 1, wherein the rinse arm includes a spray shield,
and the fluid dispenser is configured to direct rinse fluid to one or more
exposed surfaces of the spray shield.
8. The system of claim 7, wherein the spray shield has an exposed curved
surface.
9. A substrate polishing method, comprising:
supporting a substrate above a polishing surface;
dispensing slurry onto the polishing surface;
polishing the substrate against the polishing surface;
directing rinse fluid through a rinse arm toward the polishing surface; and
directing rinse fluid to one or more surfaces of the rinse arm in proximity
to the polishing surface and exposed to airborne slurry particles
generated from slurry on the polishing surface.
10. The method of claim 9, wherein the step of directing rinse fluid toward
one or more exposed surfaces of the rinse arm comprises directing moist
air in the vicinity of the exposed surfaces of the rinse arm.
11. The method of claim 9, wherein the step of directing rinse fluid toward
one or more exposed surfaces of the rinse arm comprises generating moist
air with a fine mist nozzle.
12. The method of claim 9, wherein the step of directing rinse fluid toward
one or more exposed surfaces of the rinse arm comprises maintaining the
atmosphere in the vicinity of the one or more exposed surfaces at a
relative humidity level of about 80% or greater.
13. The method of claim 9, wherein the step of directing rinse fluid toward
one or more exposed surfaces of the rinse arm comprises maintaining a
layer of liquid on the one or more exposed surfaces.
14. The method of claim 9, wherein rinse fluid is directed to the one or
more exposed surfaces while the polishing surface is being rinsed.
15. The method of claim 9, wherein rinse fluid is directed to the one or
more exposed surfaces after the polishing surface has been rinsed.
16. The method of claim 9, wherein the substrate is polished by a polishing
apparatus, and rinse fluid is directed to one or more exposed surfaces
while the polishing apparatus is idle.
17. The method of claim 9, wherein the rinse arm includes a spray shield,
and rinse fluid is directed to one or more exposed surfaces of the spray
shield.
Description
BACKGROUND OF THE INVENTION
The invention relates to substrate polishing techniques, including chemical
mechanical polishing (CMP).
Chemical mechanical polishing is a process by which a substrate surface is
smoothed (planarized) to a uniform level by a polishing pad and an
abrasive slurry. A substrate to be polished is usually mounted on a
rotatable carrier head and pressed against a moving polishing pad. The
polishing pad typically includes an abrasive surface. An abrasive chemical
solution (slurry) may be introduced onto the polishing pad to assist in
the polishing process. Typically, a rinse arm supplies rinse fluid (e.g.,
de-ionized water) to the polishing pad to remove coagulated slurry and
other material from the polishing pad surface.
SUMMARY OF THE INVENTION
In one aspect, the invention features systems and methods for polishing a
substrate with reduced contamination. A substrate polishing system
comprises: a substrate carrier; a polishing surface; and a rinse arm
having one or more nozzles configured to direct rinse fluid toward the
polishing surface, the rinse arm further having a fluid dispenser
configured to direct rinse fluid to one or more surfaces of the rinse arm
in proximity to the polishing surface and exposed to airborne slurry
particles generated from slurry on the polishing surface. A substrate
polishing method comprises: supporting a substrate above a polishing
surface; dispensing slurry onto the polishing surface; polishing the
substrate against the polishing surface; directing rinse fluid through a
rinse arm toward the polishing surface; and directing rinse fluid to one
or more surfaces of the rinse arm in proximity to the polishing surface
and exposed to airborne slurry particles generated from slurry on the
polishing surface.
Embodiments may include one or more of the following features.
The fluid dispenser may be configured to direct moist air in the vicinity
of the exposed surfaces of the rinse arm. In one embodiment, the fluid
dispenser comprises a nozzle. In accordance with this embodiment, the
fluid dispenser is configured to receive a liquid and to direct the liquid
through the nozzle to generate a fine mist in the vicinity of the one or
more exposed surfaces.
In operation, the fluid dispenser may be configured to maintain the
atmosphere in the vicinity of the one or more exposed surfaces at a
relative humidity level of about 80% or greater. The fluid dispenser may
be configured to maintain a layer of liquid on the one or more exposed
surfaces.
In some embodiments, the rinse arm includes a spray shield, and the fluid
dispenser is configured to direct rinse fluid to one or more exposed
surfaces of the spray shield. The spray shield may have an exposed curved
surface.
Rinse fluid may directed to the one or more exposed surfaces while the
polishing surface is being rinsed. Rinse fluid also may be directed to the
one or more exposed surfaces after the polishing surface has been rinsed.
In one mode of operation, rinse fluid is directed to one or more exposed
surfaces while the polishing apparatus is idle.
Among the advantages of the invention are the following. By maintaining the
atmosphere in the vicinity of the exposed rinse arm surfaces at an
elevated relative humidity level, airborne slurry particles adhering to
the exposed surfaces remain in suspension and, therefore, may be easily
cleaned, e.g., during a high pressure rinse cycle. This feature reduces
the likelihood that slurry particles will accumulate on exposed surfaces
of the polishing apparatus and flake off while a substrate is being
polished, reducing the likelihood of substrate defects caused by such
slurry contamination.
Other features and advantages will become apparent from the following
description, including the drawings and the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a perspective view of a polishing apparatus.
FIG. 1B is an exploded view of the polishing apparatus of FIG. 1A.
FIG. 2A is a diagrammatic top view of a fluid delivery system disposed over
a polishing pad.
FIG. 2B is a diagrammatic cross-sectional side view of the fluid delivery
system of FIG. 2A.
FIG. 3A is a diagrammatic side view of a fluid delivery system delivering
slurry to the surface of a polishing pad.
FIG. 3B is a diagrammatic side view of a fluid delivery system delivering
rinse fluid to the surface of a polishing pad while moist air is being
directed to rinse arm surfaces in proximity to the polishing pad and
exposed to airborne slurry particles generated as the polishing pad is
being rinsed.
DETAILED DESCRIPTION
Referring to FIGS. 1A and 1B, a polishing apparatus 10 includes a housing
12 that contains three independently-operated polishing stations 14, a
substrate transfer station 16, and a rotatable carousel 18 which
choreographs the operation of four independently rotatable carrier heads
20. Attached to one side of housing 12 is a substrate loading apparatus 22
that includes a tub 24 that contains a liquid bath 26 in which cassettes
28 of substrates 30 are immersed before polishing.
Carousel 18 has a support plate 42 with slots 44 through which shafts 46 of
carrier heads 20 extend. Carrier heads 20 can independently rotate and
oscillate back-and-forth in slots 44 to achieve a uniformly polished
substrate surface. Carrier heads 20 are rotated by respective motors 48,
which are normally hidden behind removable sidewalls 50 of carousel 18. In
operation, a substrate is loaded from tub 24 to transfer station 16, from
which the substrate is transferred to a carrier head 20. Carousel 18 then
transfers the substrate through a series of one or more polishing stations
14 and finally returns the polished substrate to transfer station 16.
Each polishing station 14 includes a rotatable platen 52, which supports a
polishing pad 54, and a fluid delivery system 80. Platen 52 and fluid
delivery system 80 are both mounted to a tabletop 57 of polishing
apparatus 10. A pad conditioner (not shown) also may be provided to
condition the surface of polishing pad 54.
For further details regarding the general features and operation of
polishing apparatus 10, please refer to U.S. Pat. No. 5,738,574, by Perlov
et al., entitled "Continuous Processing System for Chemical Mechanical
Polishing," and assigned to the assignee of the present invention, which
is incorporated herein by reference.
Referring to FIGS. 2A, 2B, 3A and 3B, fluid delivery system 80 dispenses
slurry onto polishing pad 54 to assist in the polishing process and, after
a substrate has been polished, fluid delivery system 80 delivers rinsing
fluid to polishing pad 54 to remove slurry from the pad surface. Fluid
delivery system 80 includes a rinse arm 82 having a base portion 84
disposed outwardly from the edge of polishing pad 54 and an end portion 86
disposable over polishing pad 54. Base portion 84 is mounted on a shaft 88
to enable rinse arm 82 to rotate between a processing position over
polishing pad 54 and a maintenance position adjacent to the pad. Rinse arm
82 may be angled along its length from base portion 84 to its end portion
86 (as shown), or it may be straight. Rinse arm 82 includes two slurry
delivery lines 90, 92 mounted or disposed within rinse arm 82. Preferably,
slurry delivery lines 90, 92 are formed from tubing which are coupled to
one or more slurry sources. A diastolic or other pump may be used to pump
slurry through delivery lines 90, 92.
A central rinse fluid delivery line 94 delivers one or more rinse agents to
a plurality of nozzles 96, 98, 100, 102, and 104 mounted to a lower
surface 106 of fluid rinse arm 82. End portion 86 preferably terminates at
a position short of the center of polishing pad 54 to allow substrate
carrier 20 to move radially across polishing pad 54 without the risk of
collision between rinse arm 82 and substrate carrier 20. Nozzle 104 is
disposed on end portion 86 of rinse arm 82 at an angle relative to the
plane of rinse arm 82 so that it may deliver rinse fluid to a central
region 87 of polishing pad 54. In an alternative embodiment, rinse arm 82
may extend over the center of polishing pad 54 and deliver rinse fluid to
the center of the pad through a nozzle directed downwardly from end of
rinse arm 82; the rinse arm is moved out of the way during polishing
operations. Rinse fluid is supplied to polishing pad 54 at a pressure
sufficient to remove slurry from the pad. An exemplary rinse fluid
pressure range is about 15-100 psi, and preferably about 30 psi or
greater.
Mounting shaft 88 houses slurry delivery lines 90, 92 (FIG. 3A) and a rinse
fluid channel 108 (FIG. 3B) which delivers fluid to fluid rinse arm 82.
Nozzles 96-104 are threadedly mounted in or otherwise disposed on lower
surface 106 of rinse arm 82 and are connected to rinse fluid channel 94.
Nozzles 96-104 are preferably fine-tipped nozzles configured to deliver
rinse fluid in a fan-shaped plane to reduce splashing cause by the spray
of rinse fluid against polishing pad 54. In one embodiment, nozzles 96-104
deliver rinse fluid in an overlapping pattern across the surface of
polishing pad 54 to insure that a substantial portion of polishing pad 54
receives a direct spray of rinse fluid. Nozzles 96-104 deliver rinse fluid
at polishing pad 54 with a volume and at a pressure selected to lift and
suspend (entrain) slurry particles in the volume of rinse fluid.
As shown in FIG. 2B, the rinse arm housing includes a spray shield 110
formed from two curved side walls 112, 114 that extend downwardly from
lower surface 106 of rinse arm 82 toward polishing pad 54 to confine at
least a portion of rinse fluid spray from nozzles 96-104. The lower edges
of shield side walls 112, 114 are positioned above the surface of
polishing pad 54 to allow material to pass underneath while effectively
confining a substantial amount of rinse fluid. The height of the lower
edges of shield walls 112, 114 above the surface of the polishing pad may
be adjusted. The flow rate of rinse fluid and the distance between the
lower edges of shield 110 and polishing pad 54 may be selected so that a
wave of rinse fluid may accumulate and sweep away excess material from the
surface of polishing pad 54. As polishing pad 54 rotates, rinse fluid and
excess slurry material may be swept towards the edge of polishing pad 54
where they may be collected for disposal.
Referring to FIG. 3A, in one mode of operation, slurry 115 is delivered to
polishing pad 54 from an output 116 of slurry delivery line 90. As slurry
particles--which are in a colloidal suspension--are delivered to the
surface of polishing pad 54, portions of the colloidal suspension may
evaporate or otherwise become airborne. Portions of the colloidal
suspension may also become airborne during a high pressure rinse cycle, as
rinse fluid is being delivered to the surface of polishing pad 54. This
airborne substance may adhere to exposed surfaces of the rinse arm housing
in proximity to polishing pad 54. Once adhered to an exposed surface, the
colloidal suspension tends to dry, leaving deposits which may accumulate
over time and occasionally flake off onto polishing pad 54. If such
contamination becomes trapped between substrate 30 and polishing pad 54
while substrate 30 is being polished, it would likely cause a defect in
the substrate surface.
As shown in FIG. 3B, this problem is substantially reduced by supplying
moist air 120 to rinse arm surfaces in proximity to polishing pad 54 and
exposed to airborne slurry particles. Moist air 120 maintains the
atmosphere in the vicinity of the exposed surfaces at a relative humidity
level of about 80% or greater, and preferably at a relative humidity level
of about 90% or greater, up to a relative humidity level of about 99%. At
these humidity levels, colloidal suspensions adhering to the exposed rinse
arm surfaces do not dry and, instead, the slurry particles remain in
suspension. In some modes of operation, moist air 120 maintains a layer of
liquid (e.g., deionized water) on the exposed surfaces to prevent adhered
colloidal suspensions from drying. In this way, deposits of slurry
particles do not accumulate on the exposed rinse arm surfaces, reducing
the amount of contamination that might cause substrate defects. The
exposed rinse arm surfaces may be rinsed by moist air 120 while rinse
solution is being applied to polishing pad 54. The exposed surface may
also be rinsed by moist air 120 while polishing pad 54 is being replaced,
during some other routine maintenance procedure, or while the polishing
apparatus is in an otherwise idle state.
Moist air 120 may be supplied to the exposed rinse arm surfaces in
proximity to polishing pad 54 in a variety of ways, including fine mist
generation as described below.
As shown in FIG. 3B, rinse arm 82 includes a misting nozzle 122 configured
to direct a fine fluid mist 120 in the vicinity of rinse arm surfaces in
proximity to polishing pad 54 and exposed to airborne slurry particles
generated as slurry is being delivered to polishing pad 54 and as slurry
is being rinsed from polishing pad 54. Misting nozzle 122 directs moist
air stream 120 in the vicinity of the exposed rinse arm surfaces,
including lower surface 106 and the inner surfaces of shield 110, to
prevent slurry deposits from accumulating on these surfaces. Misting
nozzle 122 may be moved to other locations on rinse arm 82, or one or more
additional misting nozzles may be installed, to provide moisture
sufficient to prevent slurries from drying on the exposed surfaces of
rinse arm 82.
As shown in FIG. 3B, misting nozzle 122 is coupled to rinse fluid supply
line 108 so that a moist air is delivered in the vicinity of the exposed
rinse arm surfaces each time rinse fluid is delivered to polishing pad 54
through nozzles 96-104. In an another embodiment, misting nozzle 122 may
be coupled to a valve and a controller (not shown) that is configured to
choreograph the delivery of rinse fluid through nozzle 122. In one mode of
operation, misting nozzle 122 supplies moist air 120 to the exposed rinse
arm surfaces after slurry has been deposited onto polishing pad 54 and
rinse arm 82 has been rotated to its maintenance position adjacent to
polishing pad 54. In another mode of operation, nozzle 122 supplies rinse
fluid to the exposed rinse arm surfaces while polishing apparatus 10 is
idle. The controller is preferably programmable to enable operators to
select the times during which nozzle 122 is supplying moist air 120 to the
exposed rinse arm surfaces.
Although a rotating polishing system has been described above, the
invention also may be implemented in connection with a linear polishing
system, such as the linear polishing system described in U.S. application
Ser. No. 08/568,188, filed Dec. 5, 1995, and entitled "Substrate Belt
Polisher," which is incorporated herein by reference.
Other embodiments are within the scope of the claims.
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